Is "poufy" a real word? Well, I'm going to pretend it is, because these little sleeves are certainly going to be poufy!
I started the sleeve construction by running double rows of gathering stitches on the sleeve cap and the sleeve bottom edge. Then I measured and cut piping the length of the sleeve bias band:
The bottom edge of the sleeve is gathered, piped, and bound with a bias strip. This sleeve is constructed in its entirety, then set into the armhole "in the round." The bottom gathers are pulled to fit the piping, matching the center and the outside edges.
Notice how the gathers are concentrated in the center of the sleeve only? This, in conjunction with the sleeve cap gathers, is what creates the "pouf" effect. There are no gathers in the underarm part of the sleeve, which also makes it more comfortable to wear.
This sleeve is already taking on the pouf shape.
I pin this together with the piping on the bottom. One thing I do when I adjust my gathers is line them up straight, as if they were pleats. I have found that if I adjust the gathers so that both rows of gathering stitches are visible (and by that I mean that they sit on the top where I can see them), I get nice even gathers instead of little pleats. If you click on the picture above, you will see the double row of gathering stitches are visible.
Here's what this looks like when I flip it over (the pins are on the bottom).
Then I use basting thread to baste it from the piping side, basting over the stitching line of the piping. This is one of the places where 5 minutes' worth of hand basting makes all the difference. Here it is all basted:
Now I stitch it with the machine, sew the underarm seam, and attach the bias band. And I have two adorable little sleeves!